357 Mag Speeds...

[Rocky Raab]

Critch, the simplest explanation between cast and swaged is this: Cast bullets are formed from molten metal poures into a mould.

Swaged bullets are made from soft lead that is high-pressure formed (cold) into shape.

Swaged bullets are almost dead soft - they have to be or they couldn't be "squozed" into form. They're excellent choices for mild target loads at low velocity and breech pressure. Target loads for the .38 Special would be a good example.

Cast bullets can be made of a variety of metal alloys (swaged are almost pure lead) using tin, antimony and/or other metals. Some of them can be so hard they'll shatter on impact.

In general, the higher the pressure of the load, the harder the bullet needed. As you originally said you wanted to shoot bullets to the highest velocity possible, swaged bullets are completely out of the question. You'll want cast bullets with an alloy of at least BHN 15 (and BHN 20 would be better) for full-velocity 357 Maggie loads.

If those 125s are swaged, forget it. Stick to 900 fps loads or less with those.

I just checked at Midway. If you bought the 125-gr truncated cone bullets listed, they are indeed hard-cast. They're of a Lyman #2 alloy equivalent, and thus should be good up to about 1500 fps as it is about BHN 15.

According to the Lyman manual, you can achieve 1500+ fps with several powders. Try 11.0 to 13.0 of Blue Dot or 13.5 to 19.5 of 2400. Work up gradually, the top loads are HIGH pressure!